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A die is weighted in such a way that each of 2,4, and 6 is twice as likely to come up as each of 1,3, and \(5 .\) Find the probability distribution. What is the probability of rolling less than 4 ?

Short Answer

Expert verified
The probability distribution for the given die is as follows: P(1) = \( \frac{1}{9} \), P(2) = \( \frac{2}{9} \), P(3) = \( \frac{1}{9} \), P(4) = \( \frac{2}{9} \), P(5) = \( \frac{1}{9} \), and P(6) = \( \frac{2}{9} \). The probability of rolling less than 4 is \( \frac{4}{9} \).

Step by step solution

01

Determine the relative probabilities

The problem has told us that each of 2, 4, and 6 is twice as likely to come up as each of 1, 3, and 5. We can represent this as a ratio: - For 1, 3, and 5: each has a relative probability of 1 - For 2, 4, and 6: each has a relative probability of 2
02

Calculate the total relative probability

We will now sum up the relative probabilities for all numbers on the die: Total relative probability = Sum of relative probabilities(1, 3, 5) + Sum of relative probabilities(2, 4, 6) = 1 + 1 + 1 + 2 + 2 + 2 = 9
03

Calculate the individual probabilities

Now, we can find the probability distribution for each possible number by dividing each relative probability by the total relative probability: Probability(1) = \( \frac{1}{9} \) Probability(3) = \( \frac{1}{9} \) Probability(5) = \( \frac{1}{9} \) Probability(2) = \( \frac{2}{9} \) Probability(4) = \( \frac{2}{9} \) Probability(6) = \( \frac{2}{9} \) So the probability distribution is as follows: - P(1) = \( \frac{1}{9} \) - P(2) = \( \frac{2}{9} \) - P(3) = \( \frac{1}{9} \) - P(4) = \( \frac{2}{9} \) - P(5) = \( \frac{1}{9} \) - P(6) = \( \frac{2}{9} \)
04

Calculate the probability of rolling less than 4

To find the probability of rolling a number less than 4, we just sum up the probabilities for 1, 2, and 3: Probability(roll less than 4) = Probability(1) + Probability(2) + Probability(3) = \( \frac{1}{9} + \frac{2}{9} + \frac{1}{9} = \frac{4}{9} \) So, the probability of rolling a number less than 4 is \( \frac{4}{9} \).

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Key Concepts

These are the key concepts you need to understand to accurately answer the question.

Relative Probabilities
When we talk about relative probabilities, we're referring to how likely each outcome is compared to another. In the case of the weighted die from the exercise, some numbers are more likely to appear than others. This isn't a fair die like in typical scenarios. Instead, it gives certain numbers twice the chance of appearing:
  • The numbers 2, 4, and 6 each have a relative probability of 2.
  • The numbers 1, 3, and 5 each have a relative probability of 1.
To find an overall picture of how likely each number is, we sum up these relative probabilities. The sum in our example is 9, derived from adding 1+1+1+2+2+2. This total helps us determine the probability distribution by showing how individual probabilities relate to each other.
Probability Theory
Probability theory is the branch of mathematics that deals with calculating the likelihood of different outcomes. It's essential for understanding and predicting the behavior of various random processes. Let's break down how it's applied:
  • Every possible outcome has a probability.
  • The probability of all outcomes combined should equal 1.

In our exercise with the weighted die, we calculated the probabilities by dividing each number's relative probability by the total sum of relative probabilities, which is 9. For example, the individual probability for rolling a 1 is \[ P(1) = \frac{1}{9} \]. The applications of probability theory allow us to understand many real-world phenomena, from simple games to complex systems, by breaking down events into smaller, manageable probabilities.
Weighted Dice
Weighted dice are specially designed to increase or decrease the chance of certain outcomes. This isn't typical for fair gameplay because it skews the natural randomness. However, weighted dice can be used in specific scenarios where certain outcomes are preferred:
  • A weighted dice gives distinct probabilities to outcomes based on assigned weights.
  • This manipulation allows for control over the likelihood of specific results.

For our weighted die, numbers 2, 4, and 6 are twice as likely to show up as numbers 1, 3, and 5. This means the probability doesn't depend solely on chance but rather on how much emphasis is placed on particular outcomes. With such understanding, we can calculate the probability of rolling any particular number and, in this exercise, determine that the probability of rolling a number less than 4 is \[ \frac{4}{9} \]. Weighted dice concepts are a marvelous way to learn about probability distributions and the impact of varying weights.

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